\documentclass[tikz]{standalone}
\usepackage{tikz}

\begin{document}
\foreach \n [remember=\n as \previous (initially 0)] in {1,...,7,0} {
		\begin{tikzpicture}[main_node/.style={circle,fill=blue!20,draw,minimum size=2em,inner sep=3pt]}]
			\node[main_node] (8) at (0:0.5) {b};
			\node[main_node] (9) at (180:0.5) {t};
			\foreach \x in {0,1,...,7}
			\node[main_node] (\x) at (360/8*\x:2) {$a_{\x}$};
			\path[draw,thick] (\n) edge (8);
			\path[draw,thick] (\n) edge (9);
			\path[draw,thick] (\previous) edge (8);
			\path[draw,thick] (\previous) edge (9);
			\path[draw,thick] (\n) edge (\previous);
		\end{tikzpicture}
	}
\end{document}
